If you live near a non-polluted source of salt water you can make your own sea salt—simply gather salt water in clean milk jugs or soda bottles, pour it into a large pot through cheesecloth and/or a sieve to remove any sand or debris, and boil until 90% of the water has evaporated. Then pour the thick salt water (it should look like wet sand) into a shallow baking pan and leave uncovered for 3-5 days, stirring occasionally.

Culinary blog How-to Baker used 6 gallons of water which yielded around 6 cups of sea salt. The author notes that the time spent boiling is 1-1.5 hours per gallon of water boiled and also points out that boiling the water will kill any bacterial malefactors that may be lurking in the water. For step-by-step photos and detailed instructions visit the source link below.